Next story in Science

Video: Hawaii volcano could violently erupt

Transcript of: Hawaii volcano could violently erupt

BRIAN WILLIAMS, anchor:Geologists on the
Big Island
are warning
Hawaii
's
Kilauea volcano
could awaken into violent explosions and eruptions at any time. The main concern, of course, the 5,000 people a day who visit the lava flows and the volcanic rock. US scientists are saying it's hard to predict when it's going to enter its next explosive phase.

A band of ancient warriors were en route to battle near the summit of Mount Kilauea more than 200 years ago when Pele, the Hawaiian goddess that lives inside the volcano, got angry. Very angry.

Searing rocks exploded from Kilauea's summit crater and a thick current of lava surged toward the warriors, propelled by hurricane-force winds. More than 400 people died, according to historical estimates, in the deadliest volcanic eruption in what is now the United States.

"There have been more powerful eruptions here, but none more deadly," said Don Swanson, a geologist with the Hawaiian Volcano Observatory.

Kilauea's legendary eruption happened in November 1790, but until now the deadly surge of lava associated with it had yet to be identified, Swanson said during a news conference Tuesday at the annual meeting of the American Geophysical Union in San Francisco.

"We think that we've identified the very eruption, by its deposit, that was responsible for the deaths of so many people," Swanson said. And this eruption points to a more explosive past for Kilauea than thought.

Fieldwork also turned up footprints in the muddy ash not far from the Hawaiian observatory, Swanson said.

"One wonders if those footprints were the last that that person took," Swanson said.

Eruptive spectrum
By carbon-dating explosive deposits and lava flows, Swanson built an eye-opening timeline of the volcano's history. Advancements in radiocarbon dating, along with dogged fieldwork, allowed Swanson to date tiny pieces of carbon, a task that wasn't possible just a few years ago

"He's found many, many more explosions than we thought existed," said Ken Hon, a volcanologist at the University of Hawaii at Hilo.

Violent eruptions are not synonymous with Kilauea. Its name means "spewing" or "much spreading" in Hawaiian and the volcano has been continually oozing out lava since Jan. 3, 1983. People often walk near these sluggish rivers of lava that flow down the mountain's slopes and into the ocean. These "gentle eruptions" are rarely a threat unless people are doing something foolish, Swanson said, but that hasn't always been the case.

Over the past 2,500 years, Kilauea has existed on the opposite end of its eruptive spectrum — in an explosive period — about 60 percent of the time, according to Swanson's new data.

"The major finding that we have is that these are not infrequent events," Swanson said.

Explosive again?
Kilauea is currently in a lava flow mode, as it has been for the other 40 percent of the past 2,500 years. During these quieter periods, the volcano begins to rebuild itself by piling lava flow on top of lava flow. Kilauea, however, could switch back to an explosive period without much warning, Swanson said, because scientists don't fully understand how these explosions begin. These powerful and dangerous volcanic periods can last hundreds of years.

"We don't know when the next period of explosive activity may start," Swanson said. "Is it a threat today? Ithink the answer is clearly yes," Swanson said.

Whenever Kilauea returns to an explosive mode, a long-term evacuation of the summit, a popular vacation spot, will be necessary.

After 9,000 years of dormancy, the Chaiten volcano in southern Chile awoke in 2008 and began a series of eruptions that spewed ash miles into the sky, as shown in this image. The volcano's namesake town of 4,500, just 6 miles from the spewing crater, was devastated by falling ash and floods. The eruption claimed at least one life and serves as a stark reminder that slumbering volcanoes pose grave dangers. Click on the "Next" label to learn about seven more dangerous volcanoes around the world.

Is Mount Vesuvius the most dangerous?

Courtesy of Digital Globe

Italy's Mount Vesuvius is most famous for the A.D. 79 eruption that buried the cities of Pompeii and Herculaneum. Despite the dark history, millions of people today live near the volcano. The thriving mass of humanity in such close proximity to the volcano makes Vesuvius a serious contender for the world's most dangerous volcano. Scientists fear that a catastrophic eruption could hurl scalding gas-rich magma, water vapor and debris at the masses with insufficient warning time for an evacuation.

Mexico City, a metropolis of 18 million people, sits 40 miles to the east of Popocatepetl, the second tallest volcano in North America. Puebla, a town of 2 million, lies 30 miles to the west. A major eruption, scientists say, could choke the skies with ash and send massive mudslides into the crowded valleys below. The result could prove catastrophic. The volcano has been relatively quiet since a bout of activity between 1920 and 1922, though it rumbled back to life in 2000, as shown in this image, prompting evacuation orders and worries that "Popo" is ready to blow.

Will spirits warn when Merapi is ready to go?

Afp
/
AFP/Getty Images

Merapi in Indonesia is one of the world's most active volcanoes, regularly spewing hot gas and ash miles into the sky, and sending mud and fragmented rocks down the sides. In 1994, 60 people were killed by a searing gas cloud, and about 1,300 people died when it erupted in 1930. During a bout of eruptions in 2006, many villagers, including the woman in this picture, refused orders to evacuate. They believe the spirits will warn when a catastrophic eruption is imminent.

Nyirangongo threatens with fast moving lava

NASA file

Lava flows, while hot, are rarely deadly: They usually ooze slow enough that people can easily outrun them. That's not the case with the lava that flows from Nyirangongo in Africa's Democratic Republic of Congo. It has very low levels of silica, the mineral that thickens and slows lavas. In 2002, Nyirangongo's lava suddenly gushed at speeds up to 60 mph into the town of Goma, which is home to half a million people. Scientists fear that lava pooling in the crater could suddenly drain again and cause even more devastation.

After nearly a year of minor earthquakes and eruptions, Colombia's Nevada del Ruiz volcano exploded on Nov. 13, 1985. Pyroclastic flows melted the summit's snowcap. Mudflows, called lahars, raced down the mountainside. One mudflow wiped out the village of Chinchina and killed 1,927 people, according to reports. A second followed the same path as earlier lahars and swept away the town of Armero, shown in this image. An estimated 23,000 people died, making it Colombia's worst natural disaster. Scientists said an early warning system could have averted the loss of life. Now that one is in place, will it work when the volcano wakes again?

Is majestic Mount Fuji overdue for an eruption?

Shizuo Kambayashi
/
AP file

The islands of Japan harbor more than 100 volcanoes, and a handful or so erupt every year. The majestic Mount Fuji, shown here, has not erupted since 1707, but a swarm of low-frequency earthquakes in 2000 and 2001 raised the specter that the mountain was awakening from its 300-year slumber. Though Fuji has since quieted down, the risk to Tokyo, a city of 30 million people just 70 miles to the east, is very real, scientists say. A 2004 government study put the price tag of a worst-case eruption at more than $20 billion.

Mount Rainier, an attractive danger

Lyn Topinka / USGS

Washington's 14,410-foot-tall Mount Rainier, shown in this image, is a big attraction for many people in the Pacific Northwest. It is also a big threat, according to scientists. An estimated 3 million people live in its shadow — at least 100,000 on top of old mudflows from previous eruptions. The flows, known as lahars, are the greatest risk. Though commonly associated with major eruptions that strike with ample warning, an earthquake or small burp of rock, ash and gas could also trigger a lahar, giving residents in the path only 10 to 15 minutes to escape.